You appear to have two totally unrelated questions... you don't say
how many miles are on the car to even consider flushing the tranny.
Did you look in your owners manual at the factory recommended
items. If you did, did you see anything about FLUSHING THE
TRANSMISSION? No. You don't flush it! Now the second
question... Usually, when the power steering pump squeals it is due to
low fluid level. CAREFULLY top it up to the fill line with the correct oil
per your owners manual.